OFFSET
1,2
COMMENTS
a(21) > 10^4.
MAPLE
select(k -> isprime((2*k+1)*k!+1), [$0 .. 300])[];
MATHEMATICA
Do[If[PrimeQ[(2*k + 1)*Factorial[k] + 1], Print[k]], {k, 0, 3000}]
PROG
(PARI) for(k=0, 3000, if(isprime((2*k+1)*k!+1), print1(k", ")))
(SageMath)
for k in range(3000):
if is_prime((2*k+1)*factorial(k) + 1):
print(k)
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Reza K Ghazi, Jun 07 2021
STATUS
approved